Buses are used to transmit data from a device to one or more other devices. Interconnects (e.g., on chip interconnects) are used to transmit data form one function on a chip (e.g., microprocessor) to one or more other functions on the chip. Switching data on a bus or interconnects is a significant source of power consumption.
In high-performance microprocessor designs power consumption is a critical concern, and bus/interconnect power is a large component. Microprocessors that include several processor cores on a single die may require long (traverse a long distance across the die) and wide (large number of parallel bits) buses as interconnections. Each time a bus line is switched, the entire capacitance of the metal wire must be charged or discharged, as well as the capacitance of the repeaters which are inserted along the bus to reduce the delay. Both of these capacitances can be quite large, thus the switching,power is significant.